Recently, electrochemical cells have actively been researched. A fuel cell, for example, out of the electrochemical cells, includes a system to generate power, by electrochemically reacting a fuel such as hydrogen and an oxidizing agent such as oxygen.
Among them, a polymer electrolyte membrane fuel cell (PEFC: Polymer Electrolyte Membrane Fuel Cell) has been put into practical use, as a stationary power source for domestic use and a power source for automobile, since a load to the environment is small.
As a catalyst layer contained in each electrode of the PEFC, a carbon carried catalyst in which a catalyst material is carried by a carbon black carrier is generally used.
The carbon carrier is eroded with the power generation of the fuel cell, the deterioration of the catalyst layer and a membrane electrode assembly (MEA: Membrane Electrode Assembly) containing the catalyst layer is large, and thereby a large amount of catalyst is used so as to ensure durability of the fuel cell. One of the large problems for spreading a PEFC is cost reduction by reducing a used amount of noble metal catalyst.
In order to avoid the catalyst deterioration by a carbon carrier, and to enhance catalytic activity and property of an electrochemical cell, a carrier-less porous catalyst layer has been proposed, and excellent durability and high property thereof have been ensured even with a small amount of platinum.
But the property of these catalyst layers is sensitive to variation of the operation environment. When the catalyst layer like this is applied to a cathode side of a fuel cell, the property is greatly deteriorated sometimes due to the humidity of air supplied to the fuel cell. As its measure, an improvement of a catalyst layer structure may be considered, but the robustness thereof is not sufficient yet, and a further improvement is required.